<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>

    <style>

        * {
            margin: 0px;
            padding: 0px;
        }
        /* .demo1 {
            width: 190px;
            height: 190px;
            background-color: purple;

        }

        .demo1 div {
            width: 100px;
            height: 100px;
            background-color: yellow;
        } */
        /* div {
            width: 300px;
            height: 200px;
            background-color: purple;
        }

        .demo1 {
            margin-bottom: 100px;
        }

        .demo2 {
            background-color: pink;
            margin-top:300px;
        } */

        /* .father {
            width: 500px;
            height: 500px;
            background-color: pink;
            overflow: hidden;
        }

        .father div {
            width: 200px;
            height: 200px;
            background-color: purple;
            margin-top: 50px;
        } */

        /* .son {
            width: 200px;
            height: 200px;
            background-color:purple;
            margin-top: 50px;
            margin: 50px 50px 50px 50px;
        } */

        /* .father {
            width: 300px;
            height: 200px;
            background-color: pink;
        }

        .son {
            padding-left: 100px;
            background-color: purple;
        } */

        div {
            width: 312px;
            height: 312px;
            margin: 100px auto;
            border: 1px solid red;
            border-radius: 50%;
        }
    </style>
</head>
<body>
    <!-- <div class="demo1">
    </div>
    <div class="demo2">

    </div> -->

    <!-- <div class="father">
        <div class="son"></div>
    </div> -->

    <!-- <div class="father">
        <div class="son">123</div>
    </div> -->


    <div></div>
</body>
</html>